B-Alaninebetaine is confined to species of the Plumbaginaceae (Hanson et al, 1994). It is synthesized by direct N-methylation of the amino acid B-alanine, catalyzed by S-adenosylmethionine (SAM)-dependent N-methyltransferases (Hanson et al, 1991; 1994; Rathinasabapathi et al, 2000; 2001). In contrast to glycinebetaine synthesis, B-alaninebetaine does not require oxygen (Hanson et al, 1994). It is possible, therefore, that this pathway represents an adaptation to anoxic saline environments (Hanson et al, 1994). The B-alaninebetaine biosynthesis pathway is active in both leaves and roots of B-alaninebetaine-accumulating Limonium species (Hanson et al, 1991). The precise origin of B-alanine remains obscure. This amino acid is apparently not derived from decarboxylation of aspartate in Limonium species (Hanson and Burnet, 1994).

Hanson AD, Burnet M 1994 Evolution and metabolic engineering of osmoprotectant accumulation in higher plants. In "Cell Biology: Biochemical and Cellular Mechanisms of Stress Tolerance in Plants", NATO ASI Series H (JH Cherry ed), Springer, Berlin, pp. 291-302.

Hanson AD, Gage DA 1991 Identification and determination by fast atom bombardment mass spectrometry of the compatible solute choline-O-sulfate in Limonium species and other halophytes. Austr. J. Plant Physiol. 18: 317-327.

Hanson AD, Rathinasabapathi B, Chamberlin B, Gage DA 1991 Comparative physiological evidence that beta-alanine betaine and choline-O-sulfate act as compatible osmolytes in halophytic Limonium species. Plant Physiol. 97: 1199-1205.

Hanson AD, Rathinasabapathi B, Rivoal J, Burnet M, Dillon MO, Gage DA 1994 Osmoprotective compounds in the Plumbaginaceae: A natural experiment in metabolic engineering of stress tolerance. Proc. Natl. Acad. Sci. U.S.A. 91: 306-310.

Rathinasabapathi B, Fouad WM, Sigua CA 2001 beta-Alanine betaine synthesis in the Plumbaginaceae. Purification and characterization of a trifunctional, S-adenosyl-L-methionine-dependent N-methyltransferase from Limonium latifolium leaves. Plant Physiol. 126: 1241-1249.

Rathinasabapathi B, Sigua C, Ho J, Gage DA 2000 Osmoprotectant beta-alanine betaine synthesis in the Plumbaginaceae: S-adenosyl-L-methionine dependent N-methylation of beta-alanine to its betaine is via N-methyl and N,N-dimethyl beta-alanines. Physiol. Plant. 109: 225-231.